Caulk, adhesive, potting material and other fluid materials are commonly contained in tubular cartridges having an outlet nozzle at one end and an opposite open end that is closed by a wiper slidably seated against the inside face of the cartridge wall. The material is discharged from the outlet nozzle by advancing the wiper through the cartridge toward the nozzle, which increases the static pressure of the contained material sufficiently to overcome back pressures against such flow. Special mixing or routing conduits if connected to the outlet nozzle add to the outside back pressure. The force needed for moving the wiper depends on factors including the outside back pressure, the viscosity of the contained material, and the size of the cartridge.
Conventional dispensing tools utilize a plunger connected to a rod, and a power device activated by a control trigger forces the rod and plunger axially into the open cartridge end and against the wiper. Many dispensing tools are hand held and portable, being powered manually by a ratchet mechanism indexed incrementally upon each trigger squeeze or pneumatically by an air cylinder.
Our U.S. Pat. No. 5,263,614 issued on Nov. 23, 1993 discloses manual dispensing tools having spring linkages between the intermittently activated power ratchet device and incrementally advanced driven plunger, for storing and dissipating unused energy inputted to the device for maintaining substantially continuous forces on the plunger, even between successive trigger squeezes. This overcomes many problems associated with discharging an incompressible contained material by means of such a tool.
Our U.S. Pat. No. 5,314,092 issued on May 24, 1994 discloses a specific dispensing tool plunger having a shiftable O-ring for providing a sealing-venting action to minimize leakage past the wiper and plunger when pressurizing and discharging the contained material, while yet allowing the plunger to be removed from the emptied cartridge for reuse.
Single component materials set up primarily as each is discharged from its single cartridge. Multiple component reactive fluid material systems blend different components together in precise ratios to form an intended composite material, each separate component being stable alone but reacting to set up after being mixed together. The reaction or setting time will vary, but most commonly is short, as measured in minutes. Common multiple component reactive material systems include two-part epoxies, urethanes, silicones, phenolics, acrylics and polyesters.
Existing multiple component reactive material systems commonly use separate component cartridges held side-by-side, and interconnect the adjacent outlet nozzles via a common mixing tube having a single discharge outlet. The cartridges are commonly of equal length, and component cartridges of the same or different diameters would provide the specific needed component ratio. The advance of the plungers in unison through the cartridges would force the proportioned components together initially for blending in the mixing tube and discharge then from the tube outlet nozzle as the intended composite material.
Intermittent tool usage is common and the material volume used will vary during any particular Job. This means that material contained in the cartridge(s) and mixing tube/discharge conduit can begin to or do over time set up, making use of the remaining contained material questionable or impossible. Mixing tubes are accordingly made as throw-away items, intentionally sacrificing the material contained therein. Continued use or reuse of the material cartridge however is preferred, for realizing material cost savings to the users.
However, in most reactive material systems, the adjacent cartridge nozzles are interconnected via the inlet to the mixing tube, and one component can cross over via the mixing tube inlet and enter the cartridge of the other component, starting premature mixing of the components in the cartridge itself. That possibly is particularly enhanced as the cartridge nozzles are the same size and shape and the component pressures at the cartridge nozzles can instantaneously differ substantially during changing flow or discharge conditions; and considering that the viscosities of the separate components can differ substantially, such as having a pasty base component and a free-flowing liquid catalyst component, and that the volumetric ratio of base to catalyst component can vary widely, such as being 1:1, 3:1 or even 10:1.
This premature mixing can present a serious problem during intermittent tool usage, should a tool nonuse period exceed the reactive setting time and a glob of set material form in one cartridge and plug its outlet nozzle, making that cartridge unusable. Premature component mixing further could throw off the needed precise component mixing ratios, producing a different composite material no longer having the desired physical properties of the intended composite material. Disposal of partially emptied material cartridges because of premature setting can be quite costly for user of the material(s).
Our above-identified application Ser. No. 08/154,623 now abandoned discloses a check valve insert suited for use at the paired outlet nozzles of reactive component cartridges, the check valve having adjacent openings seated over the outlet nozzles and having a reed overlying and resiliently closing the openings except for when component pressures are being generated within the cartridges sufficient to cause intended discharge.